1496
All the other brands went along
(slrpnk.net)
This is a most excellent place for technology news and articles.
USB-C is fairly open, and USB4 can do most things Thunderbolt 3/4 can do, but there are exceptions like daisy-chaining. Thunderbolt 5 is also out now, and it has no open counterpart. And Thunderbolt is very much proprietary, requiring licensing and certification from Intel.